Control system for lifting apparatus



Sept. 29, 1959 c. A. BALEs ET Ax. 2,906,249

CONTROL SYSTEM FOR LIFTING APPARATUS I Filed Oct. 21, 1957 INV ENTORS lUnited States Patent G CONTROL SYSTEM FOR LIFTING APPARATUS Charles A. Bales, Gary, and Hans O. Linde, Michigan City, Ind., assignors to United States Steel Corporation, a corporation of New Jersey Application October 21, 1957, Serial No. 691,247

8 Claims. (Cl. i12b-'46) This invention relates to a system for regulating the operation of lifting apparatus in accordance with the weight of a load being handled thereby. More particularly it relates to a system for regulating the pressure of hydraulic fluid supplied to, and thereby the lifting power developed' by, hydraulic lifts of the type used, for example, to position coils of strip with respect to the man- .dreIs of winding and uncoiling reels at the ends of strip processing lines.

In continuous strip processing lines, coil handling operations incidental. to charging or removal of a coil of strip Arequire carefuladjustment of its position, particularly in a vertical direction, with respect to winding or uncoiling mandrels. For this purpose, lifts are provided for the reel mandrels at the exit and entry ends of a line, and

are commonly mounted on buggies or cars used for trans porting the coils. Since the coils normally handled have sizes that Yvary over wide limits, such lifts must be designedv for the largest coil, and lifts capable of handling loads in the nature of 100,000 pounds are therefore used for coils that weigh only a few thousand pounds. This ,means in the case of hydraulic lifts, that the pressure ofthe hydraulic Huid supplied to the lift motor is the same for smaller loads as that used for heavier loads. Because of the excess of lifting force or power that is .available when handling coils of smaller size, improper ornaccurate operation of the coil lifting apparatus may t result in serious damage to the reeling mandrels and the operating mechanism therefor.

OneY of the principal objects of this invention is to provvide. a control system for hydraulically operated coil lifts and the like that will protect reeling mechanism in strip processing lines from damage as the result of excess lifting capacity. A related and more general object of the vinvention is to provide a control system for regulating the power of a lift in accordance with therweight of a load being handled thereby. A further and more specific object of the invention is to provide a control system for `hydraulic lifts which will regulate the pressure of hyd'raulicY iluid supplied to the lift motor according to the weight of the load being handled.

Another object of the invention is to provide a control system for regulating the operation of hydraulically operated coil lifting apparatus, which comprises a compression Cell that. includesanA electrical strain gage subject to the Weight of the load being handled, and a control valve vt'iperate'd byA thestrain. gage for regulating the pressure di hydraulic iluid. supplied to the lift motor proportion- Figure 2 is a sectional view taken substantially along the line II-lI of Figure l; and

Figure 3 is a diagrammatic sketch of the control system of this invention.

The drawings show, as a preferred embodiment, the manner in which the control system of this invention is applied to a hydraulic lift on a buggy that is used to transport coils of metal strip to and from the reeling apparatus of a strip processing line. In this showing, a coil reeling apparatus 1 is shown somewhat diagrammatically with its mandrel 2 extending axially through an opening centrally of a coil C. During raising and lowering movement relative to the mandrel 2, the coil C is supported on a platform 3 mounted for vertical movement on a supporting frame 4. The frame 4 is part of a carriage or buggy that is used for transporting coils to and from a strip processing line and has flanged wheels (not shown) for movement over trackway rails.

The mounting of the platform 3 on the carriage frame 4 comprises a hollow depending slide 5 that is received in and has a guided rectilinear vertical movement in a guide housing 6 carried by the frame 4. Vertical movement is imparted to the slide 5 and platform 3 by an expansible chamber hydraulic motor 7 extending axially of the housing 6 and slide 5. The motor 7 includes a cylinder 8 that has a pivotal connection 9 at its lower end with a thrust plate 10 and a piston rod 11 projecting axially from its upper end. The piston rod 11 has a pivotal connection 12 with the upper end of the guide 5 so that its movement to and from an extended position relative to the cylinder 8 is effective to impart vertical movement to the guide 5 and the platform 3. Hydraulic fluid is supplied to and exhausted from the cylinder 8 through a conduit 13. A two position valve 14 selectively controls the connection of the conduit 13 with an exhaust sump conduit 15 and a pressure supply line 16 connected with a pump (not shown), and thereby controls the raising and lowering movement of the plat'- form 3 by the motor 7. The apparatus thus far described is conventional and forms no part per se of this invention.

For measuring the weight of a coil C on the platform 3, a strain gauge or compression cell 20 of conventional construction, and preferably one of the type designated SR-4 strain gauges that are produced by Minneapolis- Honeywell Regulator Co. of Philadelphia, Pa., is arranged between the thrust plate 10 and a stationary base plate 21 secured to the carriage 4. The thrust plate 1t) has a loose tit in the housing 6 and bears against the upper end of the cell 20, which has its lower end supported on the base plate 21, so that it is subject to and measures the load on the platform 3. For a detailed explanation of the construction of cells of this character, reference is made to United States Patent No. 2,292,549, and to the catalogue publication by the Minneapolis-Honeywell Regulator Co. entitled Instrumentation Data Sheet No. 10.18-1b. Since its construction is conventional, it will be sufficient to indicate here that the cell 20 has a wire filament or resistor, designated by the numeral 22 in Figure 3, the resistance of which changes according to the loading to which the cell 20 is subjected.

As indicated above, the system of this invention regulates the pressure of the hydraulic iluid supplied to, and thereby the power developed by the motor 7, in accordance with the weight of the load on the platform 3. Since each of the units or components of this system, including the cell 20 and its strain responsive resistor 22, has a construction that is conventional, they have been illustrated diagrammatically in Figure 3. As there shown, such system comprises a pressure regulating valve 23 in the hydraulic fluid supply line 16 which is operated by a diaphragm motor 24 to regulate the pressure supplied through the conduit 13 to the lift motor 7, the diaphragm motor 24 being actuated according to pressure supplied thereto by a pneumatic relay 25 from an air supply line 26. -The relay 25- in turn is controlled by an amplifier 27 that measures the change in resistance of the strain responsive resistor 22 and produces a proportional actuation of the relay 25 such that the pressure of the air delivered to the diaphragm motor 24 is directly proportional to the change in resistance of the strain responsive resistor 22, and thereby the weight of the load on the platform 3. In this manner, the diaphragm motor 24 is caused to actuate the pressure regulating valve 23 so that it operates to supply hydraulic uid to the motor 7 at pressures which vary directly with the weight of the load on the platform 3. Y

The components 23, 24, 25, and 27, referred to above, are conventional control devices that may be obtained from Minneapolis-Honeywell Regulator Co. in a form suitable for the purpose of this invention. The amplifier 27 is preferably a recording potentiometer of the type designated by the trade name Electronik in the above mentioned publication. The pneumatic relay 25 is preferably a pressure controller of the type designated 7021D and 704P in specification sheet 7l0-25C of the Minneapolis-Honeywell Regulator Co. The pressure regulating valve 23 and diaphragm motor 24 are preferably a series 800 diaphragm motor valve of the type shown and described in specification sheet No. 426-10M of this company. Equivalent components of conventional construction from other source that are suitable for the purposes of this invention may be used are contemplated.

In the operation of the apparatus described above, the compression cell measures the weight of the load on the platform 3 and through the control components associated therewith and effects a corresponding operation of the pressure regulating valve 23. Attention is particularly directed to the fact that the valve 23 is operated to deliver hydraulic uid to the motor 7 under pressures that are directly proportional to the weight of the load on the platform 3. While the pressure of the hydraulic fluid supplied to the motor 7 for any given loading of the platform 3 must be slightly greater than that required to elevate such load, the excess pressure required for this purpose may be provided by adjustment of the usual controls that regulate the operation of the amplifier 27. However, and since the system operates to change the hydraulic fluid pressure proportionately to the weight of the load being handled, it will be apparent that the power developed by the lifting motor 7, and thereby the lifting capacity of the apparatus, is regulated according to the size of the load being handled. In this manner, the reeling apparatus 1 as well as the hydraulic lift is protected against damage by reason of lifting capacities greatly in excess of the loads being handled.

While one embodiment of my invention has been shown and described it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

We claim:

1. In a lift of the character described, a platform for supporting a load to be lifted, motor means for raising and lowering said platform, means for adjusting the power output of said motor, and means responsive to the weight of the load on said platform for operating said power adjusting means.

2. In a lift of the character described, a platform for supporting a load to be lifted, motor means for raising and lowering said platform, means responsive to the weight of the load on said platform for producing a control force that varies with such weight, and means operated by said control force for regulating the power output of said motor means.

3. In a hydraulic lift, a platform for supporting a load to be lifted, an expansible chamber hydraulic motor including a hydraulic cylinder for raising and lowering said platform, supply means including a control valve for regulating the pressure of hydraulic fluid supplied to said motor, and means responsive to the weight of the load on said platform for effecting a proportional operation of said control valve.

4. In a hydraulic lift, a platform for supporting a load to be lifted, an electrical strain gauge subject to the weight of the load on said platform, an expansible chamber fluid pressure motor for raising and lowering said platform, and means for supplying hydraulic uid to said motor including control means operated by said strain gauge for regulating its pressure proportionally to the loading of said platform.

5. In a hydraulic lift, a stationary support, a compression cell including a strain gauge on said support, a hydraulic motor cylinder having one end bearing against said strain gauge and a piston rod projecting from its other end, a platform for supporting a load to be lifted and having a connection with said piston rod rendering it operative to impart raising and lowering movements thereto, means for supplying hydraulic fluid to said cylinder including a control valve for regulating the pressure of the fluid supplied, and means including said strain gauge for operating said control valve to vary said uid pressure proportionally to the weight of the load on said platform.

6. In a lift of the character described, a platform for supporting a load to be lifted, an electrical strain gauge subject to the weight of the load on said platform, motor means for raising and lowering said platform, and means operated by said strain gauge for regulating the power output of said motor means proportionally to the loading of said platform.

7. In a lift of the character described, a platform for supporting a load to be lifted, a control means subject to the weight of the load on said platform, an expansible chamber fluid pressure motor for raising and lowering said platform, and means for supplying uid to said motor including means operated by said control means for regulating its pressure proportionally to the loading of said platform.

8. In a lift of the character described, a platform for supporting a load to be lifted, motor means for raising and lowering said platform, means for regulating the power output of said motor means, and a control means subject to the weight of the load on said platform for actuating said regulating means to adjust the power output of said motor means proportionally to the loading of said platform.

References Cited in the file of this patent UNITED STATES PATENTS 2,227,762 Ronning Jan. 7, 1941 2,809,051 Jackson Oct. 8, 1957 2,820,647 Jackson Jan. 21, 1958 2,843,396 Lucien July 15, 1958 

